Pyrolytic conversion of hydrocarbons



Aug. 1, 1950 R. B. sMlTH PYRoLYTIc CONVERSION oF HYDRocARBoNs- FiledApril 29, 1947 mman-Ehm mul-OOO Patented Aug. 1, 1950 e n Y 2,517,140*VPYROLYTIC CONVERSION OF HYDROCARBONS l `a corporation of MaineApplication April 29, 1947, Serial No. 744,660 v l ,This inventionrelates to the pyrolytic conversion of hydrocarbons and, moreparticularly,

to pyrolytic conversion prcesses involving the use of a ilnely dividedcatalyst.

The invention is especially applicable to conversion processes of thegeneral type wherein a finely divided catalyst,y at elevatedtemperature, is suspended in olyvapors, passed to a reaction zone inwhich conversion lof the oiloccurs and in lwhichspent catalyst Yisseparated from the oil vapors,\the separated catalyststripped of oil.regenerated by burning oi coke or carbon deposited thereon, andv the'regenerated catalyst ,again suspended in the stream of oil vaporspassing to the reaction zone. Operations of the type `described arecommonly designated fluid catalyst processes. 1

In conventional, operation, the spent catalyst Vnormallypzasses from`the bottomof the reactor through a stripping column extending downward-`ly `:from thelower end of thelreactor` and in which the catalyst isAcontacted with steam for the purpose of removing. or stripping, from thecatalyst vaporizable hydrocarbons remaining `thereon. Thestrippedcatalyst passes from the j-,bottom of the stripperfand is picked up by astream of air and conveyed thereby intothe Hydrocarbon vaporsproduct ofthe conversion,

`pass* from the upper portion of the reaction zone fthrough a cycloneseparator for the separation of larger suspended catalyst particles, andfrom thence to a fractionator in which insuniciently convertedhydrocarbonsr are separated from the desired product. 40

In operations of this type, there is usually Aipresent in the catalyst,largely as a result of attrition of the catalyst during its repeatedcycling through the system, extremely nely divided particles, orso-called nes, which are carried oli *from` the reaction zo'ne insuspension in the effluent hydrocarbon ,vapors.

These finely divided particles of catalyst are extremely resistant to`conventional `methods of separation and even 1,-

persist in the product which has undergone fractionation andcondensation.

In gasoline, for instance, the presence of finely divided solids isextremely objectionable because of their tendency to form enginedeposits in internal combustion engines in which the gasoline iscustomarily used.

In my copending application Ser. No. 744,659, led concurrently herewith,I have described and claimed an improved method of separating such finesfrom the eilluent gases from the regenerator according to which thegaseous suspension is subjected to ultra-sonic vibrations by which thefines are caused to agglomerate and the agglomerates are separated as bysettling and returned to the system.

My present invention provides an improved process whereby residual nelydivided particles of catalyst may be` eiectively separated from theliquid hydrocarbon products of uid catalyst conversion operations, whichcomprises the step of subjecting the product having the nely dividedcatalyst suspended therein, and in liquid phase, to ultra-sonicvibrations of the order of about one-half megacycle per second wherebythe nely divided catalyst dispersed in the liquid is caused to coagulateto such an extent that it is readily separable from the product as bygravity settling or by conventional filtration.

The coagulation of the catalyst particles may be eiected batch-wise orcontinuously. In batch treatment, a portion of the gasoline product, forinstance, containing residual suspended catalyst, is charged into avessel in which there is in contact with the liquid gasoline adiaphragm, adapted to ultra-sonic vibration, forming a partition betweenthe gasoline chamber and a chamber containing a liquid in which there issubmerged a piezoelectric crystal of quartz, for instance, excited inthe known manner by high frequency electrical impulses.

In continuous operation, the gasoline is continuously passed throughsuch a chamber in contact with a diaphragm or diaphragms such as justdescribed. The crystal will normally be protected from temperature riseby continuously circulating the liquid fromthe chamber in which thecrystal is submerged through cooling means and back to the chamber.

The treatment of the gasoline, for instance, for the separation offinely divided catalyst 'theren from, is, with advantage, carried oncontinuously in conjunction With the catalytic conversion operation. Theinvention, accordingly, provides an improved process adapted tocontinuous operation and comprising a plurality of cooperating steps socoordinated as to constitute a unitary operation in which a charge ofcatalyst is repeatedly used and intermittently regenerated and returnedto the conversion zone and in which the conversion product is attainedsubstantially free from catalyst particles.

The present' invention is used'fwith'f particular advantage inconjunction with the invention of my previously referred to copendingVapplicationy in which catalyst fines areseparated ,fromgthe eiuent gasesfrom the regenerating operation and returned to the fluid catalystcycle. In conventional operation, a considerablelproportiono catalystnes are normallycarriedfromlthe"sys tem in suspension in the iiuegases.Where the air or other oxidizing gas introduced through conduit I0, theproducts of combustion passing from the upper portion of the regeneratorthrough cyclone type separator l2, for the separation of the largerparticles of suspended catalyst, and from which the products ofcombustion pass through conduit i3, the separated catalyst beingreturned to the dense phase body of catalyst in the regenerator.

Regenerated catalyst is Withdrawn from the bottom of the regeneratorfrom a zone above the grid lll through regenerated catalyst leg l5, inwhich fithere interposed a gli valve@ i6., advan- '-tageouslyr aeconventionalislide 'valve, i'fortthe control of the iiow of catalysttherethrough into the cflower Vend of conduit 2 where it is picked'up bya.streamsoipreheated charge oil passing to the reactor.

Flue gases Apassing from the regenerator ithroughcoriduitJi-S,I carryingcatalyst -fines in suspension,arepassed through chamber ll in whichtheyare'tsubjected to ultra-sonic vibration rines are recovered and returnedto ,theicycle as s there described, there is a greater tendency to wardthe accumulation of the catalystmesin the cycle and contamination of thefractions of thelconverted hydrocarbons thereby. -Byi-the joint use ofthe recovery-of'theflnes 1from=tiie |fiu'ei gases,f substantial economyis effected'. While avoiding A5the I presence -`of -catalyst lflinesl-i'n i the 4iiinished product.

The :invention '-Will `be further @described "and illustrated withreference-'Lto thelaccompanying .drawingvwhich represents,'conventionally -and somewhat ,diagrammatically -awaflow 1iiagram..of

ai fluid catalyst cracking. operation. embodying. `my

invention. f

...Referring-more particularlyitontheembodiment o'f .1 thednvention.shown .in ithe; draw-ing, tha apiparatusA indicated .:.by -.thereference numeral si represents .1a-generallycylindricalireactoreof;conventional type. The nely divided catalystasus- -pendedjnpil=vapors.entersttheireactor.ithrough conduit 2 extending into Lthe.reactorxanditer- .'minating .in a conical member 1,3 4of :'fsornewhat@smaller maximum Adiameter `itl'ian thefreactor k.and opening upwardlyVintozitheireactor. 4.tl'irough ya lconventional. grid, not` shown.

'.:fAs the 'hot vaporsipassfupwardly fthroughfthe reactor there :is .atendency for the catalyst to ;dr,op .out of .suspension .'.forrningfaJviso-:called .in izthe reactor, from which i; the lcatalyst:..iows

ldownwardly through the annulanspace. between the member :.3vand.Lthenyvalls ofcthe 'reactor'.

Oilzyapors,lproductscof the conversion, :rise to '.type Aseparatorll forithe removal-fof. larger .par- A.ticles .of suspended .catalyst fromsthezvapors; the -l`atter passing ptherefrom.through. v conduit-:5 and.thezseparated catalyst is Areturned-.to .the Idense phasebOdyJOf-.cataIySt initthe reactor.

.Spent catalyst vis'Lwii'hdrawn from. the. bottom of the reactorinto theAupper endrofustripper- .zatransmittedtoithefsuspension throughdiaphragm i3 forming a partition between chamber Il and the-contiguouschamber I9 in which there is a piezo-crystal adapted to be excited, inthe conrentional'umanner, by highfffrequency -\-'e1ectrica1 1impulses'-transmitte`d to fthe-crystal` f throughelectriealiconnections@[leaned-127ifY The crystal issubmergedJ-inlfa*liquilyo'ilfor instanceyand"islfprotectedfrom.temperature rise, #due @to .heat utransmittedthrough'-thei diaphragm,by,l continuouslycirculatingl .lthe liquid 1J coolingIim'e'dium,@throughflthelfchamber fl l9 .fbyemeans of -`VThecoolingliquid lalso Serves-.asl affmediumlffor transmittingxthe@vibrationsrofitheicrystal'toithe EEP-luey gases, together with`aggiorncratessof icatalyst Innes, pass ffrom'L-chamber h1212.1#through-.con`duit 26 touenlarg'd settling'vchamberm'!from lsvvhiczhlthefue:gasesipassiithrough onduitlto a stack, not shown, and theseparateda'catalyst 2passesfthroughwcnduitiZ'Sito' amel'evator-:conduit-fwherein itiisipicked upi'byafcurrentioraeration airfand carriedfu-p.lintoi storage'Joinj lzromiwhich .'.it flows'..inarlui'dize'drA statethroughileg into 'itheflower end-'of :conduit: ziwiheresitsisapickediupby thestreamLvof; hydrocarbon chargei'oil and icarri'edainto.ithercreacton together r-with ,icatalyst :fromcthe i.regenerator.vv.lThet-'Liflow .fof :catalyst lithrough leg132 is.regulatedvandlscontrolledEzby ivalvea3. .1 Hydrocarbon vaporsgproductsof akthe conver- ;sion, .1 and iicarrying-L; catalyst .s1-"mes :ein:suspension pass vthrough line.- 5 toliar:fractionatorau ,fofconventional nptype,` fromT e'which :ennva-porized eheavy hydrocarbonsaremithdrawn Ithrough line-:Ellian int ermediate.:Aproduct;isiiwithrilravvn through I:line Q36 and the .alightl@hydrocarbons rcontainingiithe desired .productliareiwithdrawnzthroughiline1:3.'5. flhel lighter rfhydrocarbons `are massed'.,through condenser 38. and; from thenceffthroughziline 139',tofseparator fdiifrom whichvtheflighter .uncond'ensed hydrocarbons 1are iiwith'drawn thruugh line 4| and the condensate is Withdrawn through-.fiAsipreviously:noted'gthe'icondensate withdrawn ffrom; theeseparatorxt,frequently'I :containsi catalyst liinesznot nreafdily'.separable vthereiromi' by :ordinaryfltratiorr means. mhet cor-idensatedspassed through chamber C43-f.iniwhichtitzisisubjectedeto :ultra-sonic@vibrations #transmitted )zito ''.'the suspension 'through-'diaphragm-SMQ .forming :aspar-'titionrbetweenitheazchamberandthezcnntiguq ous chamber` l115,'infwhichthere isa'piezo-crystal, notshovm, adapted to be `excited in theconventional manner by high `freqeuncy electricalvimlAsaresult oftheultra-sonic' vibration of the liquid suspension in chamber*4'3,'thecatalyst "fines thereinareicaused tocoagulate, forming agglomerates ofsuch size andi character that they may be separated in the conventionalmanner. The gasoline, for instance, having agglomerates suspendedtherein, is passed by line 52 from chamber 43 through a conventionallter 53 and, from thence, through line 54 to storage or furthertreatment. Instead of a lter, other conventional separating means may beused, centrifugal separation may be employed with advantage.

For simplicity, I have shown a single vibrating diaphragm in thechambers l1 and 43, respective- 1y. It will be understood, however, thata plurality of such diaphragms may be employed and are usuallydesirable. Advantageously, I employ in each of these chambers aplurality of diaphragms so designed and operated as to impart to therespective suspensions passing therethrough, vibratory energy equivalentto about 250 acoustical watts per cubic foot of volume of the chamber.

As previously noted, the ultra-sonic coagulation of the catalyst iinesin the liquid product is used, with particular advantage, in conjunctionwith the ultra-sonic agglomeration of the catalyst ilnes in the uegases. However, the agglomeration of fines in the gasoline product maybe used, with advantage, either with or without the separation andreturn to the system of fines normally present in the flue gases.

It will be understood that the herein described method of separating nesfrom the liquid fraction may also be used, with advantage, in thetreatment of liquid fractions other than that containing the desiredproduct.

It will also be understood that the utility of the present invention isnot restricted to the particular embodiment thereof herein described,but is applicable to various modifications of fluid catalyst processesin which catalyst nes are carried oif in suspension in eiuent vaporsfrom the fluid catalyst reactor.

The catalyst employed may be of the type conventionally used in fluidcatalyst processes, for instance, a silica-alumina type catalyst in nelydivided, or powdered, form. The reaction conditions may likewise bethose conventionally used in operations of this type and, as understoodin the art, the optimum temperatures and pressures employed will dependprimarily upon the type of feed stock used, the particular catalystemployed and the reaction desired.

In cracking gas oil, for instance, the reaction temperature may, withadvantage, be withinthe range of 800-1,000 F. and the pressure at thetop of the reactor within the range of about 5 to pounds per squareinch. The regeneration temperature may be within the range of 950 to1,200 F., heat for the reaction being supplied in large measure `by thehot catalyst passing into the the charge oil from the regenerator;

The invention is not restricted tothe particular means shown forgenerating the ultra-sonic vibrations or imparting the vibrations to thesuspensions but contemplates other known means for imparting energy inthe form of ultra-sonic vibrations to the respective suspensions.Further, ultra-sonic vibrations varying somewhat from the specicfrequency given may be used without departing from the spirit of theinvention and may be more or less eifective in coagulating catalystfines of some types.

I claim:

l. In a fluid catalyst process for the conversion of hydrocarbons inwhich hydrocarbon vapors at an elevated temperature are intimatelycontacted with a nely divided catalyst in a reaction zone, convertedhydrocarbon vapors pass from the reaction zone and are fractionated toform a non-residual liquid fraction which contains catalyst nes insuspension, the step of c0- agulating residual catalyst nes in thenon-residual liquid fraction by subjecting the fraction to ultra-sonicvibrations of the order of one-half megacycle per second.

2. In a fluid catalyst process for the conversion of hydrocarbons inwhich hydrocarbon vapors at an elevated temperature are intimatelycontacted with a finely divided catalyst in a reaction zone, convertedhydrocarbon vapors pass from the reaction zone and are fractionated toform a nonresidual liquid fraction which contains catalyst nes insuspension, the step of removing residual catalyst lines from thenon-residual liquid fraction which comprises subjecting the fraction toultra-sonic vibrations of the order of one-hall:` megacycle per second,whereby the catalyst nes are agglomerated and separating theagglomerates of catalyst nes from the liquid fraction by filtration.

3. In a fluid catalyst process for the conversion of hydrocarbons inwhich hydrocarbon vapors at an elevated temperature are intimatelycontacted with a finely divided catalyst in a reaction Zone, convertedhydrocarbon vapors pass from the reaction Zone and are fractionated toform a nonresidual liquid fraction which contains catalyst fines insuspension, the step of removing catalyst nes from the non-residualliquid fraction which comprises passing the suspension through aconfined zone, subjecting the suspension therein to ultrasonicvibrations of a frequency of the order of one-half megacycle per secondand of an intensity equivalent to 250 acoustical Watts per cubic foot,whereby the catalyst fines are agglomerated, and separating theagglomerates of catalyst fines from the liquid fraction by ltration.

4. In a fluid catalyst process for the conversion of hydrocarbons inwhich hydrocarbon vapors at an elevated temperature are intimatelycontacted with a finely divided catalyst in a reaction zone, convertedhydrocarbon vapors pass from the reaction Zone and are fractionated toform a non-residual liquid fraction containing catalyst fines insuspension. Spent catalyst is intermittently regenerated by burning offthe carbonaceous material deposited thereon in a regenerating zone andcatalyst fines are carried ofi in suspension in the flue gases from theregenerating zone, the improvement which comprises passing the ue gassuspension through a confined zone and subjecting it therein toultra-sonic vibrations of a frequency of the order of one-half megacycleper-second andfof anzintensityc-'equivalent to 2501acoustica1watts1percubcfoot, Whereby the catalyst nes are agglomerated, separatingtheagglomerates of.' catalyst nes from the gases andreturning theseparated .fines ,to .the reaction zone, subjecting thenone-residual-liqud,fraction from the fractionation to ulinf'a-soncvvibra-tions offa frequency of the order offone-halfmegacycle per secondandvof anintenstyzequivalent 11o-.25.0 acoustical watts per cubic foot,whereby the .catalys; fines `are agglomerated-and filter-ing. theagglomerates of catalyst nes fromihe-liquidifraction.

READING BARLOWSMITH.

REFERENCES CITED Thefollowing references are of record inY the illeV of'this paient:

Number Name Date y2,31%',734 Ralston et al. Apr; 6; 1943 2,393,554'Ogorza1y Jan; 22; 1946 2,407,371 Jahnig f Sept. 10,1946

FOREIGN PATENTS Number- Country 'DateI 5.00,-2'71.` "Great-Britain A..19139 508 675; Great. Britain June 126,191.39

Sollner et a1., The Mechanism ofCoxagllkition by-Ulmasonic Waves# Trans.Earaday, Soc. 321616,623i (19,36).

.Bergmanx.1,. ,Ultrasonicsd pp, 212-216', John Wiley; and :Sons(19.38,).

2. IN A FLUID CATALYST PROCESS FOR THE CONVERSION OF HYDROCARBONS INWHICH HYDROCARBON VAPORS AT AN ELEVATED TEMPERATURE ARE INTIMATELYCONTACTED WITH A FINELY DIVIDED CATALYST IN A REACTION ZONE, CONVERTEDHYDROCARBON VAPORS PASS FROM THE REACTION ZONE AND ARE FRACTIONATED TOFORM A NONRESIDUAL LIQUID FRACTION WHICH CONTAINS CATALYST FINES INSUSPENSION, THE STEP OF REMOVING RESIDUAL CATALYST FINES FROM THENON-RESIDUAL-LIQUID FRACTION WHICH COMPRISES SUBJECTING THE FRACTION TOULTRA-SONIC VIBRATIONS OF THE ORDER OF ONE-HALF MEGACYCLE PER SECOND,WHEREBY THE CATALYST FINES ARE AGGLOMERATED AND SEPARATING THEAGGLOMERATES OF CATALYST FINES FROM THE LIQUID FRACTION BY FILRATION.